A childhood belief about imaginary friends

When I was very small, I conjured myself an imaginary friend whom I named Rufus (though I've no idea why). I never told ANYONE about him, he would always ask me not to, I always thought he seemed really frightened at the prospect of anyone other than me knowing of him. Rufus was always changing his age, he was the same guy all the time, just at different stages of his life. He would be a tiny kid, same age as me wanting to play in the dirt and tell me silly stories about horrid things that REALLY lived in wombat holes, or a teenage kid who knew all about cricket and always watched me play, or this kind of 20-30 something scrawny adult, scruffy, unshaven, dishevelled - but who knew EVERYTHING and looked after me whenever I was scared of something. Very occasionally he would appear as an extremely old guy who had lived so long that any questions I had about dragons were adequately answered due to his first hand knowledge of this 'ancient species'.

I did have a sister so I can't really claim him as a sibling substitute, and really have no idea what part of my mind decided I needed an imaginary friend, but I loved Rufus dearly and even once I knew he really didn't exist I kept on pretending, just to cling on so he wouldn't be a complete non-entity (as I assumed he would be if I let him slip into obscurity.) I'm nearly 19 now and I still bring him out and dust him off every now and then just to make sure he still lives (And, I think because it has become psychologically reassuring)